1. Field of the Invention
This invention relates to a plastic material which is opaque to X-rays, in particular, polyurethane having a covalently linked X-ray contrast material.
2. Description of the Prior Art
Use of plastics in industry, agriculture, medicine or other applications is often tied to the question of locating and testing the material during its use. In addition in medical applications it must not only be possible to locate the implanted or applied plastics, but also the plastics must be removable from the human or animal body after a set period of time. As a rule, removal requires a further surgical procedure. Although easily locatable plastics are known, they are chemically stable and can only be removed from the human body by a surgical procedure. On the other hand, plastics are known which degrade and are removed from the body after a certain time when their purpose has been served. However, such plastics are not easy to locate.
A polyurethane which is opaque to X-rays but which is not has been disclosed biologically degradable in Derwent Abstract 87-348546/49 of WO 8707-155 which, however, is not biologically degradable. However if it were biologically degradable, highly toxic halogen derivates of isophtalic acid would be created, as a result of which the polymer would not be biocompatible. Biocompatible and/or biodegradable polyurethanes which, however, are not X-ray contrasting, have been disclosed in J. Polym. Sci., Polym. Symp. 66, pp. 259 to 268 (1979) or J. Polym. Sci., Polym. Symp. 66, pp. 239 to 257 (1979), as well as in Houben-Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], Volume E 20, Makromol. Stoffe [Macromolecular Materials], pp. 1719 to 1721 (1987).